Hi Sakamoto-san
> > Power Down Release Command (PMVR, PMDAC, RSTN, PMDA1-PMDA6)> > which are located on PW_MGMT1 / PW_MGMT3 register must be> > write again after at least 5 LRCK cycle or later on each command.> > Otherwise, Playback volume will be 0dB.> > Basically, it should be> >> > 1. PowerDownRelease by Power Management1 <= call 1.x after 5LRCK> > 1.x Dummy write to Power Management1> > 2. PowerDownRelease by Power Management3 <= call 2.x after 5LRCK> > 2.x Dummy write to Power Management3> >> > To avoid too many dummy write, this patch is merging these.> >> > 1. PowerDownRelease by Power Management1> > 2. PowerDownRelease by Power Management3 <= call after 5LRCK> > 2.x Dummy write to Power Management1/3 <= merge dummy write> >> > This patch adds dummy write when Playback Start timing.> >> > Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>> > ---
(snip)
> Please add enough descriptions that kernel's timer functionality> cannot guarantee accuracy of expiration of timer for 5 phases of word> select clock on usual serial sound interface, and my (and Mark's)> concern about missing sound wave on analog part of hardware in the> beginning of playback. Without the information, users of this codec> driver will be puzzled in their hardware test. I can easily imagine> that.> > For example, 5 phases of word select clock can be calculated:> - 0.113379 msec at 44.1 kHz> - 0.104167 msec at 48.0 kHz> - 0.026042 msec at 192.0 kHz> > Kernel's timer service doesn't work by such accurate expiration> time. At the best, 1 msec or more. On the other hand, typical drivers> for any serial sound interface starts data transmission after a> callback of .trigger.> > Essentially, kernel's timer service is designed for 'rough' expiration> to release system resources, such as socket buffer for any internet> protocol. It surely guarantees timer expiration, but not for its> accuracy.> > But Mark Brown approved your idea under a certain compromise, due to> current design of ALSA SoC part. The part includes no guarantee of> timing to enable clocks on serial sound lines between .hw_params and> .trigger, in my understanding.
Thank you for your comment, yes, it should be indicated log or comment.
I noticed other approach in response to your remarks.
I will try to use it.
Best regards
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Kuninori Morimoto